1. Field of the Invention
The present invention relates to a fluorescent medium comprising a liquid crystal host containing a dissolved fluorescent guest whose visible fluorescent intensity is dependent upon the phase or orientation of the liquid crystal host. Also, the present invention relates to fluorescent displays comprising a means for cooperatively aligning a liquid crystal material and the above fluorescent medium disposed therein.
2. Description of the Prior Art
Nematic liquid crystal materials are finding wide use in display devices such as watch faces. One difficulty with conventional nematic liquid crystal devices is that they depend on the ambient light for illumination. It would be desirable to be able to employ nematic liquid crystal materials in display devices capable of use in dark environments.
It is known that liquid crystals can be used as a matrix to orient pleochroic and fluorescent guest molecules. See G. Baur, A. Stieb, and G. Meier, Polarized Fluorescence of Dyes Oriented in Room Temperature Nematic Liquid Crystals, Molecular Crystals and Liquid Crystals, 22:261 to 269 (1973); R. D. Larrabee, Fluorescence Switching by Means of Liquid Crystals, RCA Review, 34:329 to 336 (2973); G. Baur, A. Stieb and G. Meier, Quenching of Fluorescence at the Nematic-Istropic Phase Transition, J. Appl. Phys., 44(4):1905 to 1906 (1973); and U.S. Pat. No. 3,960,753. However, the interaction between liquid crystal hosts and dissolved fluorescent dyes currently is not susceptible to extrapolation and therefore operable liquid crystal/fluorescent material compositions cannot be predicted. See U.S. Pat. No. 3,960,753.